1. Field of Invention
The present invention relates to a light emission element and a light reception element for optical data communication, and to an optical transceiver module using the light emission element and the light reception element.
2. Description of Related Art
In order to make high-speed modulation possible for a surface emission laser used for optical communication, sometimes, a method of mounting by flip chip bonding without utilizing a wire is adopted. According to this method, since an upper surface side of a semiconductor laminate of a surface emission laser is mounted by a solder bump, etc., laser light is emitted from a lower surface side of the semiconductor substrate.
However, since the wavelength emitted from a common surface emission laser is 850 nm, this method is subject to a disadvantage in that, when a gallium arsenide substrate is used, it is impossible to transmit the laser light.
Herein, in order to address or overcome the aforementioned problem, a method of making the wavelength of a surface emission laser to be 970 nm has been suggested in “IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 11, NO. 1, JANUARY 1999, p128-130”. According to this suggestion; it has become possible to transmit the laser light even when the gallium arsenide substrate has been used.
However, when the wavelength has been 970 nm in accordance with the aforementioned suggestion, since the sensitivity of a PIN photodiode of silicon, which is used for the light reception side, has been reduced, it has been necessary to use a PIN photodiode of expensive InGaAs.
Regarding the surface emission laser which is a light emission element, it is necessary to make the light emission region, to which a current is applied, narrow in order to address or resolve a problem of heat generation, especially in the case where arraying is performed. Accompanying this, the method is subject to a disadvantage in that the radiation angle has been increased and, therefore, the connection efficiency has been reduced. Although it has been attempted to form a lens at an upper surface of the light emission portion in order to reduce the radiation angle, it has been difficult to precisely form a lens having a small curvature radius at a short distance from the light emission portion.
Furthermore, regarding the photodiode which is a light reception element, it is necessary to reduce the element capacity in order to realize the high-speed operation thereof. Accompanying this, the method has been subject to a disadvantage in that the connection efficiency with a fiber or a laser has been reduced.
Regarding the optical transceiver module for optically connecting the light emission element that includes the surface emission laser and the light reception element that includes the photodiode, it has been necessary to reduce the radiation angle of the laser light emitted from the surface emission laser and to increase the light reception area of the photodiode as much as possible.